School of Mathematics and Statistics - Research Publications

Permanent URI for this collection

http://hdl.handle.net/11343/294

Filters

2021 2
Reset filters

Settings
Statistics
Citations
Start date: 2020 × End date: 2021 × Author: Clisby, Nathan ×

Search Results

Now showing 1 - 2 of 2
  • Item
    No Preview Available
    Off-lattice and parallel implementations of the pivot algorithm
    Clisby, N ; Ho, DTC (IOP Publishing, 2021-12-09)
    Abstract The pivot algorithm is the most efficient known method for sampling polymer configurations for self-avoiding walks and related models. Here we introduce two recent improvements to an efficient binary tree implementation of the pivot algorithm: an extension to an off-lattice model, and a parallel implementation.
  • Item
    Thumbnail Image
    Technical note: On comparing greenhouse gas emission metrics
    Enting, I ; Clisby, N (COPERNICUS GESELLSCHAFT MBH, 2021-03-26)
    Abstract. Many metrics for comparing greenhouse gas emissions can be expressed as an instantaneous global warming potential multiplied by the ratio of airborne fractions calculated in various ways. The forcing equivalent index (FEI) provides a specification for equal radiative forcing at all times at the expense of generally precluding point-by-point equivalence over time. The FEI can be expressed in terms of asymptotic airborne fractions for exponentially growing emissions. This provides a reference against which other metrics can be compared. Four other equivalence metrics are evaluated in terms of how closely they match the timescale dependence of FEI, with methane referenced to carbon dioxide used as an example. The 100-year global warming potential overestimates the long-term role of methane, while metrics based on rates of change overestimate the short-term contribution. A recently proposed metric based on differences between methane emissions 20 years apart provides a good compromise. Analysis of the timescale dependence of metrics expressed as Laplace transforms leads to an alternative metric that gives closer agreement with FEI at the expense of considering methane over longer time periods. The short-term behaviour, which is important when metrics are used for emissions trading, is illustrated with simple examples for the four metrics.